Anode assembly



Dec. 5, 1961 E. P. ANDERSON ANODE ASSEMBLY Filed Feb. 8, 1961 FIG. I

FIG.2

I Imam INVENTOR.

EDWARD P. ANDERSON United States Patent Ofiice 3,011,959 Patented Dec.5, 1961 3,011,959 ANODE ASSEMBLY Edward P. Anderson, Livingston, N.J.,assignor to Engelhard Industries, Inc., Newark, N.Y., a corporation ofDelaware Filed Feb. 8, 1961, Ser. No. 87,974 6 Claims. (Cl. 204-147)This invention relates to an anode assembly for use in connection withcathodic protection systems for metal structures wetted by anelectrolyte as e.g., ship hulls, metal tanks or the like and, moreparticularly, to such an anode consisting of a disc of metal, preferablyplatinum or its alloys, supported by a fiat body portion of plasticmaterial, e.g. polyester resin, and secured to the metal structure to becathodically protected.

The polyester resins, frequently reinforced by fiber glass, ascustomarily used for the supporting structure of such anodes, show anappropriate combination of mechanical, chemical and dielectricproperties suitable for the purpose. However, in the case of ship hullswhich are constantly exposed to sea water, caustic soda is formed as adecomposition product of sea water by the current used in cathodicprotection, and the caustic soda attacks the polyester resin of theanode structure. Where anode assemblies of this or similar materials aresecured to the hull by studs, the studs are welded and, therefore,electrically connected to the hull. Whenever sea water comes intocontact with the studs, decomposition of the sea water occurs andcaustic soda is generated. The caustic soda attacks and damages thepolyester. Anodes of the kind described are customarily mounted flushagainst a neoprene blanket which, in turn, is mounted on the hull. Thepoints of exposure of the studs to sea Water are surrounded by plasticmaterial maintained in close contact with the blanket, whereby the seawater, when it has penetrated into the annular spaces surrounding thestuds, is practically stagnant and, as a consequence, the concentrationof generated caustic soda is comparatively high thereby causingdeterioration of the plastic support.

It has been found that the damage to the plastic anode support can beelfectively prevented by passing the electrolyte across the front andrear surfaces thereof.

In accordance with the present invention, spacing members are mountedbetween the plastic anode support and the wetted surface of the hull,which is generally covered by a neoprene blanket. By inserting spacingvmembers between the body portion of the anode support and the hull, orits blanket, respectively, a channel is formed for the electrolyte,which is sea water in the case of ship hulls, to circulate aroundsubstantially all surfaces thereof, thereby washing away any causticsoda generated in the vicinity of the plastic support, for example onthe surfaces of the steel studs securing the plastic support in place.

According to one embodiment of the invention, such spacing membersconsist of projections upon the surface of the plastic support facingthe metal object to be protected, e.g., a ship hull.

The invention will be further illustrated 'by reference to theaccompanying drawing in which:

FIGURE 1 is a top view of one embodiment of an anode assembly, and

FIGURE 2 is a cross section through the center of the anode of FIGURE 1.

A disc 4 of noble metal, preferably of platinum or an alloy thereof,having a diameter of about 7 inches, is mounted in a circular recess,having tapered Walls, provided in the body portion or supportGfabricated from plastic material, suitably a polyester resin, andhaving a substantially flat, circular shape. By means of a lead-inconductor 8 passing through a center bore 19 of the supporting bodyportion 6, electrical connection is made between the anode disc 4 andthe positive pole of the current source of the cathodic protectionsystem located within a ship to be protected. The conductor 8, passingthrough a center bore in the disc 4, is welded 0r secured thereto as at12, or in any other suitable manner to assure electrical contact.

The circular ring portion of the support surrounding the recess and thedisc 4 is provided with, for example, six bores 14 and counterbores 16which receive the studs to secure the support 6 to a ship hull. Plasticdiscs 18 are fitted into the counterbores to increase the electricalresistance between the platinum anode 4 and the studs.

According to the invention, the electrolyte is passed alongsubstantially the whole of each surface of the body portion 6. Thiscondition was not obtained before since anodes of the described typewere mounted flush against the ship hull, generally against a neopreneblanket thereon. The present invention provides spacing members insertedbetween the hull or the neoprene blanket on one side, and the surface ofthe body portion 6 on the other side. The spacing members which arepreferably pro jections on the surface of the body portion facing thehull, cover only a portion of the entire surface, providing a channelbetween the anode and the hull whereby the generated caustic soda iswashed away by electrolyte passing through the channel.

In accordance with one embodiment of the invention illustrated in thedrawing, the spacing members consist of three ring shaped bosses 20surrounding three of the stud holes 14. A further or another spacingmember is represented by three raised strips 22 radially arranged towardthe stud holes and including the area'thereof. This arrangement servesat the same time to mechanically reinforce the plastic body portion 6.

It will be apparent that either one or the other type of spacing membersmay be used alone for one anode support 6. In other words, oneembodiment of the invention would include three or six rings 20 formingthe spacing members, with the raised strips 22 being omitted. Inaccordance with another embodiment, the plastic support 6 may beprovided with the raised strips 22, but without the rings 20.

It should be noted that with the provision of three or six rings 20, onecontinuing space remains between the support '6 and the hull of theship, so that sea water may freely circulate around practically all ofthe surfaces of the support. Referring to the embodiment shown by theraised strips 22, three separate compartments are formed between thesupport and the hull by the Y-shaped structure formed by strips 22. Ithas been found that in spite of the fact that only one, and mostly two,of the compartments are under a direct influence of the streaming seawater, a washing action actually occurs even in the compartment facingin a direction opposite to the flow of sea water. This action is due tointernal friction by which the Water contained Within the compartment isentrained into movement by the water flow along both sides of thecompartment.

Spacing members in the form of the rings 20 or the raised strips 22, aswell as the combination of both as shown in FIGURE 1, have been found tobe advantageous, since they permit the anode assembly to adapt moreeasily to the curved shape'of ship hulls.

A further projection 24 may be provided at the center of the anodeassembly on the surface facing the hull and cooperates with the currentlead-in device mounted on the ship hull.

It will be obvious to those skilled in the art that many modificationsmay be made Within the scope of the prescut invention without departingfrom the spirit thereof, and the invention includes all suchmodifications.

This application is a continuation-in-part of application Serial No.714,998, filed February l3, 1958 and now abandoned.

What is claimed is:

1. In an anode assembly for cathodically protecting a metal objectwetted by an electrolyte wherein a substantially fiat body portion ofinsulating material which supports the metallic anode is secured to thewetted surface of the metal object, the improvement which comprisesmeans including spacing members mounted between the body portion and thesurface of the metal object for maintaining substantially the whole ofeach surface of the body portion in contact with the electrolyte,whereby the electrolyte is allowed to circulate between the metal objectsurface and the body portion.

2. In an anode assembly for cathodically protecting a metal objectwetted by an electrolyte wherein a substantially fiat body portion ofinsulating material which supports the metallic anode is secured to thewetted surface of the metal object, the improvement which corn-' prisesmeans including projections upon the surface of the body portion facingthe metal object for maintaining substantially the whole of each surfaceof the body portion in contact with the electrolyte, whereby theelectrolyte is allowed to circulate between the metal object surface andthe body portion.

3. In an anode assembly for the cathodic protection of the hull of aship, a corrosion resistant sheet metal anode, a fiat insulating plasticsupport for said anode mounted on the hull in an essentially parallelrelationship therewith, and means for both spacing said support from thehull and providing a separating zone between said support and the hull,said zone being open to communicate with the surrounding space, wherebythe electrolyte is allowed to circulate between the hull surface and theinsulating plastic support. a

4. In an anode assembly for c'athodically protecting metal objectswetted by an electrolyte wherein a substantially fiat body portion ofinsulating plastic material which supports the metallic anode and hasstud holes therein is secured to the wetted surface of the metal objectby studs, the improvement which comprises bosses on the surface of thebody portion facing'the metal object, the bosses surrounding-the studholes and maintaining the insulating material body portion in spacedrelationship to the metal object surface, whereby the electrolyte isallowed to circulate between the metal object surface and the bodyportion.

5. In an anode assembly for cathodically protecting metal objects wettedby an electrolyte wherein a'substantially fiat body portion ofinsulating plastic material which supports the metallic anode and has.stud holes therein is secured to the wetted surface of the metal object,the improvement which comprises raised strips radially arranged towardthe stud holes on the surface of the body portion facing the metalobject, the strips including the area adjacent the stud holes and saidstrips maintaining the insulating material body portion in spacedrelationship to the metal object surface, whereby the electrolyte isallowed to circulate between the metal object surface and the .bodyportion.

6. In a method for cathodically protecting a metal ship hull wetted bysea water wherein a positive potential is impressed upon an anodesupported by a body portion of insulating plastic material, theimprovement whichcomprises, during the impressing of the positivepotential upon the anode, maintaining the insulating plastic materialbody portion in spaced relationship to the ship hull surface, andcontinuously circulating the sea water through the space between thehull surface and the plastic body portion, thereby washing away causticsoda generated in said space in the vicinity of the plastic bodyportion.

Wagner. Ian. 8, 19'57 Preiser Oct. 2 7, 1959

1. IN AN ANODE ASSEMBLY FOR CATHODICALLY PROTECTING A METAL OBJECTWETTED BY AN ELECTROYLTE WHEREIN A SUBSTANTIALLY FLAT BODY PORTION OFINSULATING MATERIAL WHICH SUPPORTS THE METALLIC ANODE IS SECURED TO THEWETTED SURFACE OF THE METAL OBJECT, THE IMPROVEMENT WHICH COMPRISESMEANS INCLUDING SPACING MEMBERS MOUNTED BETWEEN THE BODY PORTION AND THESURFACE OF THE METAL OBJECT FOR MAINTAINING SUBSTANTIALLY THE WHOLE OFEACH SURFACES OF THE BODY PORTION IN CONTACT WITH THE ELECTROLYTE,WHEREBY THE ELECTROLYTE IS ALLOWED TO CIRCULATE BETWEEN THE METAL OBJECTSURFACE AND THE BODY PORTION.